of a New Hygrometer, 



109 



only necessary to subtract the absolute dryness shown in 

 the second column of the Table (headed, Dew-point Hygro- 

 meter) from the temperature of the shade. * 



The length of this article prevents me from entering into 

 a detailed account of the extensive use which may be made 

 of the instrument I have submitted to the public ; since 

 by knowing the temperature of the shade, both the relative 

 and absolute humidity of the air can be easily ascertained 

 by very simple calculation. Sir John Leslie has well ob- 

 served, that, " The Hygrometer is an instrument of the 

 greatest utility, not only in meteorological observations, 

 but in aiding domestic economy, in regulating many pro- 

 cesses of art, and in directing the purchase and selection of 

 various articles of produce. It will detect, for instance, 

 the dampness of an apartment, and discover the condition 

 of a magazine, of an hospital, or of a sick-ward. Most 

 warehouses require to be kept at a certain point of dryness, 

 which is higher or lower according to the purposes for 

 which they are designated. The printing of linen and cot- 

 ton is carried on in very dry rooms ; but the operations of 



